1. Field of the Invention
The present invention relates generally to a radio frequency identification (RFID) tag, which is increasing in frequency of use and importance, and a widely-spread mobile terminal, and in particular, to a mobile terminal circuit including an RFID tag in one body and a wireless identification method using the same.
2. Description of the Related Art
An RFID transponder, or an RFID tag, was developed by United States National Laboratory for Department of Agriculture for the purpose of identifying livestock. An electric code for identifying an animal is recorded in a RFID tag, and then inserted into or attached to the animal. An interrogator (or a reader) for reading the electric code is installed in a cattle shed to conveniently monitor whether an animal has returned. The reader transmits an RF (Radio Frequency) signal to the RFID tag, and then, an electric code recorded in the RFID tag is delivered to the reader after being modulated by a modulator in the RFID tag. This procedure is called “backscatter modulation.” The RFID tag has an antenna coil to transmit the modulated signal to the reader therethrough. An early such system is well disclosed in U.S. Pat. Nos. 4,075,632 and 4,360,810.
Over time, technology for identifying a moving object has been applied to additional fields other than cattle management. For example, such technology has been applied to a vehicle, a container vessel, a railcar, etc., and information recorded in an RFID tag of such transportation means is used in tracking a position of the transportation means and identifying the contents of freight. Such applications and related arts are well disclosed in U.S. Pat. Nos. 4,739,328, 4,782,345, 4,786,907, 4,816,839, 4,835,377, and 4,853,705.
Recently, RFID technology is tested in various fields, and among the various fields, a communication system has attracted public attention due to its various possible applications. For example, since a mobile communication system holds a great number of subscribers, it can easily make profits by commercializing an application service based on the RFID technology. Currently, a mobile communication system has been saturated in terms of an earning rate, so service providers are eagerly searching for new application services capable of creating additional profits.
If RFID technology is introduced into the mobile communication system, it is expected that various additional services for a cellular environment can be provided. Accordingly, it is most urgently necessary to combine current RFID devices to a current cellular system.
Related prior art is disclosed in WO 01/39103 A1, WO 03/025834 A1, an IEEE paper entitled “RF Rendez-Blue: Reducing Power And Inquiry Costs In Bluetooth-Enabled Mobile Systems,” (E. S. Hall, D. K. Vawdrey, and C. D. Knutson, in Proc. 11th IEEE Int. Conf. Comput. Communications and Networks (ICCCN), Miami, Fla., October 2002.) and Korean Patent Publication No. 2002-0090929.
WO 01/39103 A1 discloses a mobile terminal in which an identification (ID) module is added between an RF block and an antenna, and the mobile terminal includes a Bluetooth module. The ID module includes a mixer, and the mixer converts a backscatter type message transmitted from the ID module to a reader at an RFID frequency of 2.45 GHz into a baseband message before transmission so that it can be processed in a computer, or transmits the backscatter type message to a base station over a traffic channel specified by a mobile communication standard or a Bluetooth channel. This technology is characterized by connecting an independent ID module to an existing mobile terminal circuit via a mixer. Through this, a base frequency band, i.e., an exiting traffic channel or Bluetooth channel, is used as an RFID frequency band. Therefore, a combination between heterogeneous circuits is not described herein.
WO 03/025834 A1 discloses a mobile terminal combined with an RFID reader, in which information is transmitted and received over a frequency band of the mobile terminal. However, the reference does not mention that instead of the RFID reader, an RFID tag can be combined with the mobile terminal. In addition, since combination between the RFID reader circuit and the terminal circuit is not disclosed, one skilled in the art cannot predict a combination of the RFID tag circuit and the terminal circuit in the light of the connection between the RFID reader circuit and the terminal circuit.
The IEEE paper discloses a structure for connecting an RFID module to a Bluetooth module in parallel in order to reduce an initial processing time of the Bluetooth module, and this is very different from a single-body type structure proposed by the present invention.
Korean Patent Publication No. 2002-0090929 discloses technology in which an independent smart card sends data to a main processing unit (MPU) of a mobile terminal. However, the reference fails to propose the connection between the smart card and the MPU or its peripheral circuit. That is, it is nothing more than simply arranging an independent circuit and a processor in one device.
The above references mainly disclose parallel connection between an RFID module or tag and a terminal circuit, or propose resource sharing in terms of frequency. However, the conventional technologies have the following disadvantages.
First, it is difficult to achieve miniaturization of a mobile terminal. Although an RFID tag can be implemented through combination of one chip with an antenna coil, it must be implemented in a smaller size to meet a general tendency toward miniaturization of the mobile terminal.
Second, since the conventional RFID tag does not have its own power supply, electromotive force induced from a carrier of an RFID reader is used as electric power. In this case, it is difficult to provide sufficient electric power to the RFID tag in an environment where an air environment between the RFID reader and the RFID tag is influenced by noises. |As a result, the RFID tag may operate incorrectly.